Melatonin, the over-the-counter sleep aid has some effectiveness.

Melatonin, the synthetic hormone that is sold over the counter, has long been a popular remedy for insomnia and jet lag. Classified in the U.S. as a dietary supplement, melatonin has been subjected to multiple studies. A review of all these studies, published recently in the BMJ, the British Medical Journal, found melatonin to have some effectiveness for adults and children with certain sleep disorders. Most of the studies compared people taking melatonin with those taking a placebo.

In adults with insomnia, melatonin allowed them to fall asleep faster, on average about 12.7 minutes faster than the people taking a placebo. In children with insomnia, melatonin worked even better. They fell asleep 17 minutes faster.

Melatonin was particularly effective for people whose circadian rhythm (the body clock's natural wake-sleep cycle) is out of whack--shift workers and people with jet lag. In people with these problems, melatonin produced sleep onset that was 38.8 minutes faster.

The doses used in these studies ranged from 0.1 mg to 10 mg for adults and children. Melatonin also increases the total time spent sleeping. This sums up the good news from this review of all relevant studies.

Here's where melatonin fell down on the job: it had no effect on sleep quality, wakefulness, or the percentage of time spent in REM sleep (rapid eye movement sleep is the mentally active stage of sleep when dreaming occurs).

In short, melatonin increases the length of time spent sleeping but did not improve sleep quality.

Melatonin is a hormone that is produced by the pineal gland in the brain. It has a role in regulating the body's natural wake-sleep cycle, initiating sleep. The body's levels of melatonin increase as exposure to light increases.

The melatonin products sold in pharmacies and health food stores are synthesized from the amino acid tryptophan. Certain foods, such as oats, rice, and sweet corn, contain melatonin in tiny amounts.